An aggressive cancer cell phenotype is the result of a variety of genetic and epigenetic alterations leading to deregulation of intracellular signaling pathways (Ponder, Nature 411:336 (2001)). However, the commonality for all cancer cells, is their failure to execute an apoptotic program, and the lack of appropriate apoptosis due to defects in a normal apoptosis mechanism is a hallmark of cancer (Lowe et al., Carcinogenesis 21:485 (2000)). Most current cancer therapies encompassing chemotherapy, radiation and immunotherapy indirectly induce apoptosis in cancer cells. Therefore, the inability of cancer cells to execute an apoptotic program due to defects in a normal apoptotic mechanism is thus often associated with an increase in resistance to chemotherapy, radiation, or immunotherapy-induced apoptosis. Primary or acquired resistance of human cancer of different origins to current treatment protocols due to apoptosis defects is a major problem in current cancer therapy (Lowe et al., Carcinogenesis 21:485 (2000); Nicholson, Nature 407:810 (2000)). Accordingly, current and future efforts towards designing and developing new molecular target-specific anticancer therapies to improve survival and quality of life of cancer patients must include strategies that specifically target cancer cell resistance to apoptosis. In this regard, targeting critical negative regulators that play a central role in directly inhibiting apoptosis in cancer cells represents a highly promising therapeutic strategy for new anticancer drug design.
While studies on various cancer-targeting substances are progressing to fight cancer, in the case of terminal cancer, most of the target therapies are used to prolong life, rather to fight cancer. One of these studies shows that a variety of cancer metabolic regulators are helpful in anticancer treatment. The basis of this study is that universal metabolic characteristics specific to cancer are targeted. For example, this means that cancer cells prefer lactate fermentation rather than breakdown of glucose into carbon dioxide and water, like the Warburg effect. For this reason, when glycolysis is interrupted to reduce the Warburg effect, cancer cells are starved, and thus are harder to grow or die.
Bcl-2 family proteins are known as a class of central negative regulators in apoptosis (Adams et al., Science 281:1322 (1998); Reed, Adv. Pharmacol. 41:501 (1997); Reed et al., J. Cell. Biochem. 60:23 (1996)). Bcl-2 is a basic member of the family, and was first isolated as a product of an oncogene. The Bcl-2 family, now, encompasses both of anti-apoptotic molecules such as Bcl-2 and Bcl-XL, and pro-apoptotic molecules such as Bax, Bak, Bid and Bad. Bcl-2 and Bcl-XL are overexpressed in various types of human cancer (e.g., breast cancer, prostate cancer, colorectal cancer, lung cancer, etc.) including non-Hodgkin's lymphoma, caused by chromosomal translocations (t14, 18) inducing the overexpression of Bcl-2. This suggests that a variety of cancer cells types, depending on increased levels of Bcl-2 and/or Bcl-XL, maintain another cellular derangement such that the cancer cells are defined as cancer cells or pre-cancer cells, and attempt to carry out apoptosis pathways. Further, increased expression of the Bcl-2 family protein is recognized as the basis of the expression of resistance to radiation and cancer-therapeutic drugs inducing cell death by various pathways in tumor cells. It is considered that Bcl-2 and Bcl-XL play a role in migration and invasion, and thus metastasis of tumor cells (Amberger et al., Cancer Res. 58:149 (1998); Wick et al., FEBS Lett, 440:419 (1998); Mohanam et al., Cancer Res. 53:143 (1993); Pedersen et al., Cancer Res., 53:5158 (1993)). It seems that the Bcl-2 family protein provides tumor cells having a mechanism for existence in a new and non-replicable environment (e.g., metastatic regions), and contributes to the organospecific pattern of the spread of clinical metastatic cancer (Rubio, La Invest. 81:725 (2001); Fernandez et al., Cell Death Differ. 7:350 (2000)). It is further considered that anti-apoptotic proteins such as Bcl-2 and/or Bcl-XL regulate cell-cell interaction through, for example, the regulation of cell surface integrins (Reed, Nature 387:773 (1997); Frisch et al., Curr. Opin. Cell Biol. 9:701 (1997); Del Bufalo et al., FASEB J. 11:947 (1997)). For this reason, therapeutic strategies for targeting Bcl-2 and Bcl-XL in cells have been widely examined to recover cancer cells sensitivity and overcome resistance of cancer cells to apoptosis (Adams et al., Science 281:1322 (1998); Reed, Adv. Pharmacol. 41:501 (1997); Reed et al., J. Cell. Biochem. 60:23 (1996)). Currently, there are ongoing Bcl-2 antisense therapies, which are several phase III clinical trials for treating solid and non-solid tumors.
Gossypol is a double biphenolic compound naturally derived from crude cottonseed oil (Gossypium sp.). Clinical trials for gossypol as a male contraceptive show safety in the long-term administration of this compound (Wu, Drugs 38:333 (1989)). Also, recently, it was known that gossypol has an anti-proliferative effect (Flack et al., J. Clin. Endocrinol. Metab. 76:1019 (1993); Bushunow et al., J. Neuro-Oncol., 43:79 (1999); Van Poznak et al., Breast Cancer Res. Treat. 66:239 (2001)). It was recently shown that (−)-Gossypol and a derivative thereof are potent inhibitors of Bcl-2 and Bcl-XL, and have a powerful anticancer activity (U.S. Patent Application No. 2003/0008924).
Phenformin, which is a biguanide-based drug such as metformin, is known as an antidiabetic agent. However, as it has been known that biguanide-based drugs including phenformin are effective for treatment of p53 gene-deficient cancer by activating AMP-activated protein kinase (AMPK), which is a crucial enzyme for physiologically regulating carbohydrate metabolism and lipid metabolism, research on the anticancer effect of a phenformin drug was conducted to demonstrate the probability of the anticancer effect of phenformin (Effect of phenformin on the proliferation of human tumor cell lines. Life Sciences, 2003 Dec. 19: vol. 74 (issue 5): 643-650.; Potentiation of antitumor effect of cyclophosphamide and hydrazine sulfate by treatment with the antidiabetic agent, 1-phenylethylbiguanide (phenformin), Cancer Let. 1979 October; 7(6):357-61.). While the anticancer effect of each of the phenformin and gossypol has been known, a synergic anticancer effect of the actions of these drugs has not been known yet.
Therefore, from the result of research on the development of substances for exhibiting a more potent anticancer effect, the inventors demonstrated that the combination of gossypol as an ALDH inhibitor and biguanide-based phenformin exhibits a considerable synergic anticancer effect, unlike other substances, and thus completed the present invention.